In the manufacture of integrated circuits (IC's), aluminum is a choice metal for fill applications. TiN may also fulfill this function for future Cu metalization schemes. Currently, titanium nitride (TiN) is used to prevent the diffusion of Al into the substrate. TiN is also used as an adhesion layer for a subsequent CVD-tungsten process or in the production of anti-reflective coating applications. Presently as chip geometries shrink, smaller contact/via geometries are necessary. In order to accommodate the smaller geometries a reduced barrier thickness in the bottom of the via is desired to maximize the area of the via occupied by the primary conductor. It is also desired to process IC's at higher temperatures for Al fill applications.
One conventionally known deposition technique is sputter deposition. In sputter deposition, a target of material, such as a metal target, is positioned in a vacuum chamber generally opposite a substrate which is to receive a layer or plug of target coating material. A working gas is introduced into the vacuum chamber proximate the target and is electrically excited to create a gas plasma including positively charged gas ions. The target is negatively biased and the positvely charged plasma species bombard the negative target, thus dislodging target material or "sputtering" the target. The dislodged or sputtered material is deposited onto the substrate surface and covers the substrate surface to fill any contacts formed in the exposed substrate surface.
Current processes sputter deposit a TiN barrier layer which undergoes a subsequent ex situ anneal to provide sufficient diffusion barrier properties for Al fill applications. TiON films are known to provide diffusion barrier properties which are superior to TiN without the need for an ex-situ processing step.
The use of in situ TiON diffusion barriers increases manufacturing throughput by eliminating the ex-situ anneal step. Capital costs are also decreased due to the elimination of the equipment relating to the ex-situ anneal step. While the known TiON films improve throughput and decrease costs, they are known to degrade the crystalline structure of the interconnect metal such as Al or Cu which is subsequently deposited. Similarly, the oxidation of a TiN barrier surface due to exposure to the atmosphere prior to the deposition of the Al interconnect is known to degrade the texture of the Al. The degradation of the aluminum is believed to decrease the interconnect reliability because of reduced electromigration lifetimes.